In conventional copying machines, printers, or like image forming apparatus, an electrostatic latent image is formed on a photosensitive body and developed with toner. The tone image is then transferred onto a recording medium, such as printing paper, and fixed under the heat and pressure applied to the recording medium carrying the toner image thereon while the recording medium is passing through a nip section formed by fixing members (e.g., a heating roller and a pressure roller) of a fixing device. Some molten toner and/or paper particles could stick to the fixing members after the recording medium has passed between the fixing members for the fixing of the toner image. It then would follow that residual toner may stain an image.
To address this problem, a solution is being proposed whereby a cleaning roller or web is brought into contact with the fixing members to collect toner.
Japanese Patent Application Publication, Tokukai, No. 2011-215587 discloses a fixing device that includes: a contact roller for contacting a pressure member with a web intervening between the roller and the member; and a depressurizing mechanism for modifying the site where the pressure member press-contacts the fixing members. The contact roller follows the motion of the depressurizing mechanism so as to maintain a constant position, direction, and pressure throughout the contact with the pressure member. The nip section of the fixing device is heated during fixing. However, the contact roller needs to be heated more than it should be because the contact roller is always in contact with the nip section and acts as a heat sink. This extra heating requirement is an obstacle to energy saving. Besides, the heat transfer to the contact roller leads to non-uniform temperature distribution in the pressure member, which is undesirable.
Japanese Patent Application Publication, Tokukai, No. 2009-122554 discloses a fixing device that includes: a roll-shaped sheet section and a cleaning roller. A heating roller is in contact with one of the surfaces of the sheet section, whereas the cleaning roller is in contact with the other surface of the sheet section. The cleaning roller is structured capable of moving into contact with, or away from, the heating roller. The cleaning roller is disposed where it is in contact with the heating roller while printing paper is passing between the rollers and it is separated from the heating roller while printing paper is not passing between the rollers. In this fixing device, no consideration is paid to a mechanism that separates the heating roller and a pressure roller, so residual toner could move to the pressure roller which has a lower temperature than the heating roller.
The present invention, to address these problems, has an object to provide a fixing device, as well as image forming apparatus, capable of preventing a temperature drop due to heat absorption by distancing the cleaning roller during fixing.